No functional changes have been made to signing, with solely slight API
changes being made.
Technically not actually FROST v5 compatible, due to differing on zero
checks and randomness, yet the vectors do confirm the core algorithm.
For any valid FROST implementation, this will be interoperable if they
can successfully communicate. For any devious FROST implementation, this
will be fingerprintable, yet should still be valid.
Relevant to https://github.com/serai-dex/serai/issues/9 as any curve can
now specify vectors for itself and be tested against them.
Moves the FROST testing curve from k256 to p256. Does not expose p256
despite being compliant. It's not at a point I'm happy with it, notably
regarding hash to curve, and I'm not sure I care to support p256. If it
has value to the larger FROST ecosystem...
Also updates Bulletproofs from C to not be length prefixed, yet rather
have Rust calculate their length.
Corrects an error in key_gen where self was blamed, instead of the
faulty participant.
Adds helper functions to verify and, on failure, blame, which move an
unwrap from callers into multiexp where it's guaranteed to be safe and
easily verified to be proper.
Closes https://github.com/serai-dex/serai/issues/10.
Saves ~8% during FROST key gen, even with dropping a vartime for a
constant time (as needed to be secure), as the new batch verifier is
used where batch verification previously wasn't. The new multiexp API
itself also offered a very slight performance boost, which may solely be
a measurement error.
Handles most of https://github.com/serai-dex/serai/issues/10. The blame
function isn't binary searched nor randomly sorted yet.
Honestly, the borrowed keys are frustrating, and this probably reduces
performance while no longer offering an order when iterating. That said,
they enable full u16 indexing and should mildly improve the API.
Cleans the Proof of Knowledge handling present in key gen.
While all the transcript/extension code works as expected, which means,
they don't cause any conflicts, n was still capped at u64::MAX at
creation when it needs to be u16. Furthermore, participant index and
scalars/points were little endian instead of big endian/curve dependent.
